茭草还田对茭白田表水中污染物浓度的影响

为了解茭白生产过程中茭草还田对田面水体中污染物的影响及其可能产生的农田面源污染,模拟试验研究了淹水条件下不同用量(0%、0.5%、1.0%)茭草覆盖还田和与土壤混合还田对田面水体中COD、氮、磷等污染物浓度的影响。结果表明,田面表水的电导率、COD、磷、钾、铁、锰在试验初期呈明显上升,第20~30天之后逐渐下降至相对稳定状态;NH₄ ⁺-N浓度峰值出现在培养试验前10天内。电导率、COD、磷、钾、铁、锰浓度随茭草还田量的增加而增加,而NH₄ ⁺-N的浓度变化则相反;茭草覆盖还田对田面表水中电导率、COD及养分浓度的影响大于茭草与土壤混合还田;配施氮肥可明显增加田面水的电导率和NH₄ ⁺-N浓度。研究建议,采用茭草与土壤混合还田,并控制好茭草还田前期（前30天）田面水的排放。

Genetic Distance of Soybean Parents and Heterosis: Correlation Study

To understand the effects of straw returning on the pollutants in the surface water of agricultural field and the possible non-point source pollution during the production of Zizania caduciflora, a simulation experiment was carried out to study the effects of straw returningof Zizania caduciflora as mulching or mixture with soil under flooded conditions (0%, 0.5%, 1%) on the concentrations of pollutants, such as COD, N, and P in surface water of agricultural field. The results showed that: the conductivity, COD, concentrations of P, K, Fe and Mn in surface water increased obviously at the beginning of the experiment, reached a peak on the 20th-30th day, and then gradually decreased to a relatively stable state; the peak concentration of NH4 +- N in surface water appeared in the first 10 days; the conductivity and the concentrations of COD, P, K, Fe and Mn increased with the increasing amount of straw returning, while the concentration of NH4+-N decreased; the effects of straw returning of Zizania caduciflora as mulching on the conductivity, and concentrations of COD, P, K, Fe and Mn in surface water of field were greater than those of straw returning as mixture with soil; N application with straw returning could increase obviously the conductivity and NH4+-N concentration of surface water. Straw returning of Zizania caduciflora as mixture with soil is better than straw returning as mulching, and the discharge of surface water should be controlled during the first 30 days of straw returning.